Press

ABSTRACT

A hydraulic press having a stationary center platen secured to a supporting framework and a plurality of movable platens disposed above and below the center platen. The movable platens are supported from the framework by a differential gearing system comprised of fixed-length roller chains secured to the platens and engaged with variable-sized overhead sprocket wheels mounted on a common shaft. The weight of each upper platen is counterbalanced by a corresponding lower platen.

Unite States Patent Parker 1 1 Feb. 1, 1972 541 PRESS 2,941,249 6/1960 Rogers ..100/199 x 3,009,495 11/1961 Coate 1 ..100/199 X [72] Inventor. Russell A. Parker, Pasadena, Cal1f. 3,050,777 8/1962 Siempelkamp' unloo/lgg UX [73] Assignee: L & F Machine Co., Huntington Park, 3,209,405 10/1965 Loewenfeld ..100/l99 X Calif. 3,236,176 2/1966 Fischer ..l00/93 P X 3,370,526 2/1968 Parker ..l00/208 X [22] 1970 3,431,838 3/1969 Hutter ..100/93 P [21] Appl. No.2 17,690

FOREIGN PATENTS OR APPLICATIONS Related US. Application Data 1,082,728 1 H1960 Germany [63] Continuation-in-part of Ser. No. 845,341, July 28, 1969, abandoned, which is a continuation-in-part of Ser. No. 801,622, Feb. 24, 1969, abandoned.

[52] US. Cl ..100/93 P, 100/199, 100/208, 144/281 [51] Int. Cl. ..B30b 7/02, 33% 15/34 [58] Field of Search ..l00/93,I94,195, I99, 208, 100/209, 269, 270; 18/16 P, 17 P; 156/530, 583; 144/287 [56] References Cited UNITED STATES PATENTS 569,920 10/1896 Hubbell ..100/194 X 2,172,003 9/1939 Stanley et a1. ..144/281 @K ii Primary Examiner-Peter Feldman Att0mey-Christie, Parker 8L Hale [57] ABSTRACT A hydraulic press having a stationary center platen secured to a supporting framework and a plurality of movable platens disposed above and below the center platen. The movable platens are supported from the framework by a differential gearing system comprised of fixed-length roller chains secured to the platens and engaged with variable-sized overhead sprocket wheels mounted on a common shaft. The weight of each upper platen is counterbalanced by a corresponding lower platen.

20 Claims, 10 Drawing Figures MTENTEU FEB i SHEET 2- W 7 HEW s SHEEY 3 T PATENTEB FEB H1; $53 ,559

sum MP Y ma num 3.638.559

PRESS CROSS-REFERENCE TO RELATED APPLICATIONS This is a continuation-in-part of my application, Ser. No. 845,341, filed July 28, 1969, now abandoned, which is in turn a continuation-in-part of my application, Ser. No. 80l,622, filed Feb. 24, 1969.

BACKGROUND OF THE INVENTION This invention relates to a press for the forming and curing of work, such as plywood.

In the fabrication of plywood, for example, thin layers of wood are coated with an adhesive and pressed together under heat and relatively high pressure by a large-area press. Other types of panelling require relatively light curing pressures which must be carefully controlled. For example, a particular type of honeycomb sandwich panelling consists of a fragile honeycomb core pressed between thin outer panels of veneer. This type of panelling requires very light curing pressures for the laminating adhesives to achieve a satisfactory bond. A moderate increase in pressure, however, may crush the fragile honeycomb material. The presses commonly used to cure laminated panels have relatively heavy platens. When pressing the type of work requiring light pressures, particularly honeycomb materials, it is desirable to counterbalance the weight of the platens so their weight is not applied to the work.

Presently available presses having more than one platen do not effectively correct for the weight of the platens. For example, the type of press commonly used to cure laminated panelling is a single upward acting press with multiple openings or workspaces" provided by hanging intermediate platens. Hydraulic cylinders force the platens upwardly against a stationary platen to press the objects disposed within the work spaces. The weight of the lower platen is not transferred to the object disposed within the lower workspace; but the weight of each remaining platen acts on the objects below it, in addition to the pressure exerted on the objects by the hydraulic cylinders.

SUMMARY OF THE INVENTION This invention provides a multiple-platen press wherein the effective weight of each platen is counterbalanced so that uniform pressure is applied to the workpieces irrespective of the weight of the platensv The press includes a stationary center platen secured to a framework, and a movable or floating" platen disposed on each side of the center platen. The floating platens cooperate with the center platen to provide an upper and a lower workspace for receiving objects to be pressed.

Movable support means are provided for suspending the floating platens from the framework so that the weight of the upper platen is counterbalanced by the weight of the lower platen. Preferably, the support means includes an overhead sprocket wheel mounted for rotation at the top of the framework. A chain is engaged with the sprocket wheel and secured at one end to the lower platen and at the other end to the upper platen. Alternatively, the support means includes an upper sprocket wheel above the upper floating platen, a lower sprocket wheel below the lower floating platen, and an endless chain engaging the sprocket wheels and secured to the floating platens. The floating platens are preferably supported at four locations on their outer edges by the support means of this invention. Drive means, preferably hydraulic actuators coupled to the floating platens, cooperate with the chain and sprocket systems to drive the floating platens toward the center platen to press the objects disposed within the workspaces. During compression, the weight of the platens is not applied to the objects because the weight of the upper platen is cancelled by the weight of the lower platen. The center platen and the floating platens can be heated to substantially equal temperatures for curing the objects being pressed.

In a preferred form of the invention, the drive means for the floating platens includes a motor coupled to the upper sprocket wheel. Preferably, the motor is operable independently of the aforementioned hydraulic actuators. In applications using a large-area press with relatively heavy platens and workpieces, this form of the invention is preferred because it avoids the necessity of using relatively large and expensive pumping equipment for closing the press. That is, the press can be initially closed using the motor driven chain drive system. Then, the hydraulic cylinders are actuated only for the purpose of applying pressure to the workpieces in the press.

Platen adjusting means are provided for levelling each floating platen and adjusting the space between platens. In use, the spacing between each workpiece and the adjacent platen is equalized so that during operation of the press the work is subjected to uniform pressure. Preferably, the platen adjusting means comprises a separate threaded shaft secured to each end of the chain and extending through a support on its respective platen. A separate threaded nut is engaged with each shaft for supporting a respective platen, so that the elevation of each platen can be adjusted. A separate coil spring is preferably disposed between the chain and each support for equalizing the load on the objects in the workspaces.

This invention contemplates a press having a multiplicity of vertically aligned floating platens to provide workspaces for a plurality of objects to be pressed. Preferably, each additional pair of floating platens is supported from the framework by a respective chain and sprocket system. The weight of each additional upper platen is cancelled by the weight of its corresponding lower platen. As a result, each workpiece is subjected to substantially the same pressure irrespective of the weight of the platens disposed above its respective workspace.

This invention additionally provides means for simultaneously subjecting a plurality of workpieces to substantially equal pressures. In a preferred form of the invention, the support means comprises a differential gearing system wherein pairs of floating platens are supported by fixed-length chains engaged with variable-sized overhead sprocket wheels affixed to a common shaft. Alternatively, pairs of floating platens are supported by endless chains engaged with respective variablesized sprocket wheels above and below the outermost floating platens. The outermost platens are engaged with progressively larger sprocket wheels, and the sprocket wheels rotate together so that the outermost platens move toward the center platen at a faster rate of speed than the innermost platens. As a result, the press is capable of simultaneously exerting uniform pressures on a plurality of workpieces. This form of the press is particularly suitable for applying relatively light curing pressures to the workpieces because the pressure applied by the press is controllable with substantial precision.

This invention further contemplates a multiple-platen press in which the support means for each respective pair of platens moves independently of the other support means. Each pair of floating platens is preferably driven by a respective chain and sprocket system which rotates independently of the other systems. In use, the floating platens are forced toward the center platen in sequence, instead of simultaneously, because each successive platen remains stationary until contacted by the adjacent platen. Thus, workpieces having different thicknesses are rapidly pressed without requiring adjustment of the platen adjusting means prior to each work cycle. This form of the invention also permits the inner floating platens to move toward and away from the center platen while the outer floating platens remain stationary, so that relatively large openings can be provided between adjacent pairs of platens to ease the cleaning or repair of the platen surfaces.

In an alternative form of the press, the platen drive system is arranged to include means for adjusting the rate of travel of an inner set of floating platens relative to that of an outer set of floating platens. Thus, a press having two pairs of floating platens, for example, can be arranged to alternately provide a two-opening press for relatively thick workpieces, or a fouropening press for thinner workpieces' BRIEF DESCRIPTION OF THE DRAWINGS The above and other features of the invention are more fully set forth in the following detailed description of the embodiments of the invention which are presently preferred, such description being presented with reference to the accompanying drawings, in which:

FIG. I is a front elevation view of the press;

FIG. 2 is a side elevation view taken on line 2-2 of FIG. 1;

FIG. 3 is an enlarged elevation view of the platen elevation adjusting means;

FIG. 4 is a front elevation view of an alternative embodiment of the press;

FIG. 5 is a perspective view showing the operation of the press of FIG. 4;

FIG. 6 is a front elevation view of the press with an alternative embodiment of the support means and drive means;

FIG. 7 is a side elevation view taken on line 77 of FIG. 6;

FIG. 8 is a front elevation view of the press with an altemative embodiment of the drive means;

FIG. 9 is a front elevation view of an alternative embodiment of the drive means of FIG. 8; and

FIG. 10 is a sectional side elevation view taken on line [0- 10 of FIG. 9.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS Referring to the drawings, a press 10 comprises a series of laterally spaced-apart upright frames 12. Each frame includes a front vertical post 14 and a rear vertical post 16. An upper horizontal crossmember 18 connects the tops of the two vertical posts, and a lower crossmember 20 connects the bottoms of the posts. Outwardly projecting mounting feet 22 are secured to the bottom of vertical posts 14 and 16 to support the press on a floor 24.

A flat, rectangular center platen 26 is horizontally disposed inside supporting frames 12 and secured to the center of vertical posts 14 and 16. An inlet pipe 28 projects outwardly from the side of the center platen and provides a passageway for a heating medium (not shown) such as hot water or steam which is pumped into the center platen. The heating medium circulates within the platen and flows out through an outwardly projecting exit pipe 30 to an external pump and heater (not shown) for recirculation. Although the press herein described is adapted to be heated by fluidic means, it is to be understood that the press can be heated by electrical means, or that nonheated platens can be used, without departing from the scope of this invention.

A pair of flat, rectangular floating platens 32 ad 34 are horizontally disposed above and below the center platen, respectively. The floating platens are approximately half the thickness of the center platen and are somewhat flexible as compared with the rigid center platen. A second pair of opposed floating platens 36 and 38 are horizontally disposed above and below platens 32 and 34, respectively. Similarly, a third pair of floating platens 40 and 42 are disposed above and below platens 36 and 38, respectively. The floating platens and the center platen cooperate to provide a plurality of vertically aligned workspaces 44.

Heating channels are provided in the floating platens by a series of holes (not shown) bored through the width of the platens and spaced uniformly along the length of the platens. These holes are interconnected at the edges of the floating platens by inlet ducts 46 into which a heating medium such as hot water or steam is pumped. Outlet ducts 48 are mounted along the center of the back surface of each movable platen to provide an outlet for the heating medium to be returned to a pump and heater (not shown) for recirculation. Alternatively, an electric heating system may be used to heat the platens.

In most uses of the press, it is desirable to maintain the center platen and the floating platens at the same elevated temperature. This is accomplished by a conventional temperature-control system (not shown) which secures platen temperatures by thermocouples (not shown) or other types of temperature transducers.

The floating platens are supported from the top of the press by two pairs of identically constructed differential gearing systems 50 and 5] located at the front edge and the rear edge of the press, respectively. Each gearing system includes a first sprocket wheel 52, a second sprocket wheel 54 having a diameter greater than that of wheel 52, and a third sprocket wheel 56 having a diameter greater than that of wheel 54. The sprocket wheels are affixed to an outwardly projecting shaft 58 which is joumaled in an overhead pillow block 60 secured to the top of upper crossmember 18 at its frontal edge. The sprocket wheels of gearing system 51 are affixed to identical shafts 58 joumaled in a pair of pillow blocks 61 secured to the rear edge of crossmember I8. In use, the sprocket wheels make one simultaneous revolution with one revolution of the shaft.

Gearing systems 50 and 51 additionally include a fixedlength roller chain 62 engaged with sprocket wheel 52, a second fixed-length roller chain 64 engaged with sprocket wheel 54, and a third fixed-length roller chain 66 engaged with wheel 56. Roller chain 62 extends down from sprocket wheel 52, with one end of the chain secured to the edge of platen 32 and the other end secured to the edge of platen 34. Thus, platens 32 and 34 are movably supported adjacent their four corners from the overhead framework. Second chain 64 similarly supports floating platens 36 and 38 from sprocket wheel 54, and third chain 66 supports platens 40 and 42 from sprocket wheel 56. As a result of the suspension system, the weight of upper floating platens 32, 36 and 40 is effectively cancelled by the weight of lower platens 34, 38 and 42, respectively.

A plurality of upward-acting hydraulic cylinders 68 are secured to the underside of lower platen 42, and a plurality of matching downward-acting hydraulic cylinders 70 are secured to the top of upper platen 40. A transverse pin 71 secures each cylinder to one of the two horizontal crossmembers l8 and 20. A pair of cylinders 68 are disposed within the lower part of each upright frame 12, and a cooperating pair of cylinders 70 is disposed within the upper part of each frame. The force exerted by the cylinders is transferred to platens 40 and 42 through respective force-distributing spiders 72. A spider includes an outwardly projecting horizontal member 74 disposed circumferentially about the upper part of each cylinder. The sides of the horizontal member are secured to a pair of vertically disposed yokes 76. An X-shaped force-distributing member 78 is secured to each end of each yoke, and each leg of the X-shaped member is bolted to the platen. Each spider is thus secured to a platen at 16 laterally spaced attachment points. A movable hydraulic ram 80 of each hydraulic cylinder is secured by a nut 82 to the center of each spider.

A horizontally disposed endless connecting chain 84 is engaged with a pair of sprocket wheels 86 having the same diameter as wheel 56 and affixed to shaft 58 directly behind wheel 56. The connecting chain drives the frontal gearing systems 50 so that they rotate together simultaneously during actuation of the hydraulic cylinders. A pair of horizontal connecting rods 88 extend rearwardly from frontal pillow blocks 60 to rear pillow blocks 61. The ends of the rods are engaged with shafts 58 so that each frontal gearing system 50 rotates simultaneously with its respective rear gearing system 51. In use, connecting chain 84 and the connecting rods 88 maintain uniform travel at all four comers of each floating platen. During operation of the press, the center platen and the floating platens are heated to the desired temperature. Objects to be pressed are then loaded into the workspaces formed by the openings between the platens. The hydraulic cylinders, which are manifolded to a common pressure source, are then pressurized. The ram of each hydraulic cylinder moves toward the center platen to force upper platen 40 down toward the center platen while simultaneously forcing lower platen 42 up toward the center platen. The force exerted on platens 40 and 42 is transferred to the remaining floating platens via gearing systems 50 and 51, and the workpieces are squeezed as the floating platens move simultaneously toward the center platen. Heat flows into the work from the platens, and a stable temperature environment is achieved within a few minutes.

In a multiple-platen press, it is desirable to simultaneously subject each object to the same pressure. This is particularly important when honeycomb panelling is bonded because curing pressures are relatively light and must be closely controlled in order to avoid crushing the honeycomb core. The press of this invention is capable of applying light, uniform pressures because of the difierential gearing system which drives the outermost platens toward the center platen at progressively greater speed than the innermost platens. For example, platens 40 and 42, which are engaged with the largest sprocket wheel 56, approach the center platen at a greater speed than platens 36 and 38. Platens 32 and 34 are engaged with the smallest sprocket wheel 52 and travel at the slowest rate of speed. Thus, the spacing between each object and its adjacent platen is continuously equalized during operation of the press, and as a result, equal pressures are simultaneously exerted on the workpieces. The press of this invention is not limited to low working pressures. It is adaptable to the pressure requirements of the particular application.

The ends of each chain are secured to their respective platens by a platen adjusting mechanism 90 which includes an upright tubular housing 92 having a threaded outer surface. A semicircular supporting block 94 is welded to the edge of a typical floating platen 96, and is further secured to the platen by a bracket 98 and hex bolts 100 which extend through the bracket into the platen. The lower part of housing 92 extends down through a stepped bore in the supporting block. The block comprises an aperture 102 in the upper part of the block and an enlarged recess 104 in the underside of the block. A pair of hex nuts 106 are engaged with the lower part of housing 92 and adapted to be screwed up and down on the housing. A coil spring 107 is disposed about the lower end of housing 92 between hex nuts 106 and the inner surface 108 of recess 104. A square head 109 is engaged with the top of the housing, and the end of a typical roller chain 110 is fitted into a recess 112 in the top of the squarehead. The coil spring is held in compression by the combined weight of the workpiece and the platen and acts to equalize the load on the work. In operation, hex nuts 106 are screwed up and down on the housing, as desired, thereby effectively changing the length of the chain. This allows each platen to be levelled independently, and provides means for spacing the platens to compensate for different-sized loads. Thus, the spacing between each workpiece and the lower surface of its adjacent platen is equalized so that uniform pressures are exerted on the work during operation of the press.

FIG. 4 shows an alternate embodiment of the press wherein the gearing systems of FIG. 1 are rearranged, and a pair of upright platen hangers 114 and 116 are engaged with the sides of platens 32, 36 and 40. This form of the invention is particularly useful in the forming and curing of work having different thicknesses. For example, on a production run involving work of the same size, the press of FIG. 1 simultaneously presses six objects at a time without requiring adjustment of platen adjusters 90 prior to each work cycle. In addition, coil springs 107 sufficiently compensate for any slight differentials in pressure. The press of FIG. 1 can be adapted to accommodate varying thicknesses of work if each platen adjuster is properly set prior to each work cycle. There may be some applications where it is more convenient to use the press of FIG. 4 because this press avoids adjusting the space between platens at the beginning of each cycle to accommodate different-sized work.

In the press of FIG. 4, inner platens 32 and 34 are engaged with sprocket wheel 56 which is affixed to shaft 58. Intermediate platens 36 and 38, and outer platens 40 and 42, are supported from sprocket wheels 54 and 52, respectively. Sprocket wheels 54 and 52 are mounted on shaft 58 with the use of a bushing (not shown) so that they each rotate freely and independently of the rotation of shaft 58 and sprocket wheel 56.

Platen hanger 114 includes a flat, elongated, upright rod 118 with a series of vertically spaced-apart holes 120. A hex bolt 122 extends through one of the holes, as desired, and secures the rod to the side of upper platen 40. Holes enable the spacing between platens to be adjusted as desired. Rod 118 extends down adjacent the side of platen 36, and passes under a stop 124 secured to the side of platen 32 by cap screws 125. An outwardly projecting flange 126 is integral with the bottom of the rod and engages the bottom of stop 124. Platen hanger 116 is constructed in the same manner as hanger 114, and is secured to the side of platen 36. The hanger engages a second stop 128 secured to the side of platen 32. Similar pairs of platen hangers are engaged with the sides of platens 32, 36 and 40 adjacent the remaining comers of these platens. Thus, a total of eight platen hangers are used.

In operation, the openings between platens are initially set by adjusting rods 118, and work is loaded into the workspaces. The hydraulic cylinders are then pressurized, forcing platen 40 down into contact with a load 130 disposed in the opening below its lower working surface. Since the sprocket wheels of the press are adapted to rotate independently, platens 36 and 32 remain stationary during the initial downward motion of platen 40. After platen 40 contacts load 130, continued application of hydraulic pressure urges load 130 and platens 40 and 36 downward simultaneously until platen 36 contacts a load 132 disposed in the opening below its lower working surface. Finally, continued application of pressure forces loads 130 and 132 and platens 40, 36 and 32 down against a load 134 disposed above center platen 26, as shown in FIG. 5. Thus, the floating platens are moved toward the center platen in sequence, rather than simultaneously, because each successive platen does not move until contacted by the workpiece in the adjacent workspace. As a result, work is pressed on a production basis regardless of its thickness.

Downward movement of platens 40 and 36 causes platen hangers 114 and 116 to move downward in a vertical plane adjacent the sides of platens 36 and 32, respectively, as shown in FIG. 5. At the completion of a curing cycle, platens 40, 36 and 32 are raised to the position shown in FIG. 4. In this form of the invention, the force applied to platen 40 by the hydraulic cylinders is not transferred to platens 36 or 32, because the floating platens rotate independently. Therefore, this invention contemplates using platen hangers 114 and 116 to raise platens 36 and 32, respectively, during the raising of platen 40. In operation, the hydraulic cylinders raise platen 40, which raises flange 126 of hanger 114 until it engages the bottom of stop 124. Further upward motion of platen 40 raises platen 36. Platen 32 is similarly raised when flange 126 of hanger 116 engages stop 128. When platen 32 is finally raised to the desired level above the center platen, the workspaces are automatically spaced apart for the unloading of the work and the subsequent reloading for the next work cycle.

FIGS. 6 and 7 show an alternate embodiment of the press wherein the floating platens are supported from the top of the press by a pair of endless chain driven differential gearing systems at the front of the press. The gearing systems include a front upper sprocket wheel 142, a second upper sprocket wheel 144 having a diameter greater than that of wheel 142, and a third upper sprocket wheel 146 having a diameter greater than that of sprocket wheel 144. The upper sprocket wheels are mounted for rotation on the front of shaft 58 at the top of the press. Gearing system 140 further includes a first lower sprocket wheel 148, a second lower sprocket wheel 150 having a diameter greater than that of wheel 148, and a third lower sprocket wheel 152 having a diameter greater than that of wheel 150. The lower sprocket wheels are mounted for rotation on the front of an elongated shaft 154 journaled in a pair of pillow blocks 156 secured to the bottom of lower crossmember 20. A first endless roller chain 158 engages the first upper sprocket wheel 142 and extends downwardly for engagement with lower sprocket wheel 148.

Similarly, a second endless roller chain 160 engages the second upper and lower sprocket wheels 144 and 150, and a third endless roller chain 162 engages the third upper and lower sprocket wheels 146 and 152. Roller chain 158 is secured to the edges of the first pair of floating platens 32 and 34; roller chain 160 is secured to the edges of the second pair of floating platens 36 and 38; and roller chain 162 is secured to the edges of the third pair of floating platens 40 and 42. The floating platens are supported from the rear of the press by a pair of endless chain driven differential gearing systems 164 identical in construction to gearing systems 140. The sprocket wheels of gearing system 164 are secured at the top of the press to shaft 58 and at the bottom of the press to shaft 154. A horizontally disposed endless connecting chain 166 engages a pair of sprocket wheels 167 aflixed to shaft 58 directly behind each upper sprocket wheel 146, and a second horizontal connecting chain 168 engages corresponding upper sprocket wheels 170 in gearing systems 164. During operation of the press, gearing systems 140 and 164 enable the press to be rapidly closed and opened. The endless chain arrangement is particularly useful in closing large-area presses having relatively heavy platens and workpieces.

Hydraulic cylinders 68 and 70 can be used exclusively to close the press of this invention; but in many applications it becomes advantageous to use the platen drive system shown in FlGS. 6 and 7. This drive system includes a drive motor 172 mounted above the press on horizontal crossmember 18. The motor can be any source of mechanical power, such as an electric gear motor or a pneumatic drive motor, for example. A rotatable drive sprocket 174 coupled to the motors drive shaft engages an endless drive chain 176 coupled to a rotatable sprocket (not shown) secured to horizontal connecting rod 88 at the top of the press. As seen best in FIG. 7, a hydraulic line 180 from an overhead hydraulic reservoir (not shown) connects to a prefill valve 182 secured to the bottom of lower crossmember 20. Hydraulic lines 184 leading from valve 182 connect to the inlet ports of hydraulic cylinders 68. A similar prefill valve (not shown) at the top of the press below the hydraulic reservoir connects to hydraulic cylinders 70. The hydraulic cylinders are manifolded to a common pumping system (not shown) which is actuated when a solenoidoperated circuit (not shown) is closed.

During operation of the platen drive system shown in FIGS. 6 and 7, the circuit to the pumping system is initially opened and the press is closed mechanically using motor 172 to drive the floating platens toward the center platen. Operation of the drive motor drives connecting rod 88 and therefore the chaindriven gearing systems 140 and 164 in the directions shown by the arrows in F IG. 6. As the floating platens move toward the center platen, the rams from hydraulic cylinders 70 and 68 are forced down and up, respectively, toward the center platen. This movement by the hydraulic rams creates a suction through the hydraulic lines which withdraws hydraulic fluid from the overhead reservoir. The fluid then flows by gravity through the prefill valves into the hydraulic cylinders as the press is closed by the drive motor. When the press is finally closed against the objects in the workspaces, the circuit to the pumping system is closed and the hydraulic cylinders, which are now filled with hydraulic fluid, are pressurized to exert the desired amount of pressure on the objects in the press.

The motor-driven platen drive system shown in FIGS. 6 and 7 is particularly favorable in applications using large-area presses having relatively heavy platens and workpieces. A large multiple-platen press using hydraulic cylinders alone for closing the platens requires relatively expensive, large capacity pumping equipment to operate the hydraulic cylinders. For example, one large 4,000 ton-capacity press requires a hydraulic system capable of pumping hydraulic fluid at a rate of [,600 gallons per minute to open and close the platens. Use of drive motor 172 in combination with prefill valves, as shown in FIGS. 6 and 7, circumvents use of the pumping system to close the press. The pumping system is only used to apply pressure to the workpieces after the press is closed, and

consequently, relatively costly large capacity pumping equipment is not required. I

FIG. 8 shows an alternative form of a platen drive system 186 arranged to open and close a pair of outer floating platens 188 and a pair of inner floating platens 190. The floating platens are supported from the top of the press by an endless chain-driven differential gearing system which includes cooperating upper and lower large sprocket wheels 192 adjacent to each comer of the press engaged with respective endless outer platen support chains 194 for supporting the outer floating platens 188, and cooperating upper and lower small sprocket wheels 196 concentric relative to respective upper and lower large sprocket wheels 192 engaged with respective endless inner platen support chains 198 for supporting the inner floating platens 190. Preferably, the diameter of the large sprocket wheels 192 is twice that of the small sprocket wheels 196. A first clutch 199 having a first clutch wheel 200 mounted concentrically relative to a second clutch wheel 20] of the same size is secured to the front part of the press framework between the differential gearing systems. A second clutch 202 having a small clutch wheel 204 mounted concentrically relative to a large clutch wheel 206 is secured to the press framework adjacent to the small clutch wheel 200. Small clutch wheel 204 is identical in size to small clutch wheel 200 and small sprocket wheels 196, and large clutch wheel 206 is identical in size to large sprocket wheels 192. A first endless drive chain 208 is engaged at its ends with a separate large drive sprocket wheel 210 concentrically mounted adjacent to each large sprocket wheel 192 at the top of the press. The first endless drive chain 208 also engages second clutch wheel 201 of the first clutch 199 and large clutch wheel 206 of the second clutch 202 between drive sprockets 210. A second endless drive chain 212 is engaged at its ends with a separate small drive sprocket wheel 214 concentrically mounted adjacent to each small sprocket wheel 196 at the top of the press. The second endless drive chain 212 also engages first clutch wheel 200 and the small clutch wheel 204 between drive sprockets 214.

During operation of the platen drive system 186 shown in FIG. 8, the rate of travel of the inner floating platens relative to that of the outer floating platens 188 can be adjusted. If it is desired to provide a two-opening press, such as that shown in FIG. 8, the second clutch 202 is disengaged and the first clutch 199 is engaged with the output shaft of a drive motor (not shown). Thus, during operation of the drive motor, the outer and inner platen support chains 194 and 198 travel the same distance, thereby providing a two-opening press. If it is desired to provide a four-opening press, the press is closed, the first clutch 199 is disengaged, and the second clutch 202 is engaged with the output shaft of the drive motor. During operation of the drive motor the outer platen support chain 194 travels twice the distance of inner support chain 198 (because of the relative sizes of small clutch wheel 204 and large clutch wheel 206), thereby providing a four-opening press. When the press is opened, the inner floating platens 190 are positioned midway between the stationary center platen and the outer platens 188, as shown in phantom lines in FIG. 8. Thus, the platen drive system 186 permits the press of this invention to be converted back and forth between a two-opening press with relatively large workspaces for pressing relatively thick workpieces to a four-opening press with narrower workspaces for pressing a greater number of thinner workpieces.

In use, the press shown in FIG. 8 is also capable of performing in a manner similar to that of the press shown in FIGS. 6 and 7, when both the first clutch 199 and the second clutch 202 are disengaged. 1f the large sprocket wheel 192 is coupled to the output shaft of a drive motor (not shown), a four-opening press is provided in which the outer floatingplatens and then the inner floating platens are driven toward the center platen in sequence. This particular arrangement is useful in pressing workpieces having two different thicknesses. Work having one thickness is placed in the openings between platens 188 and 190, and work having a different thickness is placed in the openings between platens 190 and the center platen. After the press is closed, clutch 202 is engaged prior to opening the press. If the small sprocket wheel 196 is coupled to the output shaft of a drive motor (not shown) while the large sprocket wheels 192 and thus the outer floating platens remain stationary, the inner floating platens can be driven back and forth between their respective stationary outer platens and the center platen. This arrangement doubles the size of the workspaces between the platens for ease of cleaning or repair of the platen surfaces.

FIGS. 9 and 10 show an alternate platen drive system 216 which replaces the first clutch 199 and the second clutch 202 of the press of FIG. 8 with a planetary gear drive system which includes an outer drive ring gear 218 fixed to large sprocket wheel 192, and an inner driven gear 220 fixed to an elongated central drive shaft 222. The inner driven gear 220 has a diameter equal to one-half that of the outer drive ring gear 218. Small sprocket wheel 196 is fixed to the front of drive shaft 222, and large sprocket wheel 192 is fixed to a tubular drive shaft 223 disposed concentrically about a rear portion of drive shaft 222 and arranged to rotate relative to shaft 222. The planetary gear drive system further includes a slidable clutch plate 224 mounted concentrically of shaft 222 between the large sprocket wheel 192 and the small sprocket wheel 196, idler drive gears 226 fixed to the clutch plate by respective pins 227, and a separate reverse idler drive gear 228 fixed to the clutch plate by a pin 229 and arranged to permanently engage each idler drive gear 226. A clutch lever 230 coupled to the clutch plate is adapted to slide the clutch plate longitudinally relative to drive shaft 222 between a first position (shown in FIG. 10) in which the clutch plate is locked to the press framework 232 by cooperating frame lock dogs 234, and a second position (not shown) in which the clutch plate is locked to inner driven gear 220 by cooperating drive lock dogs 236.

During operation of the planetary gear drive system, a twoopening press is provided by engaging the clutch plate 224 in its first position. In this arrangement, the clutch plate remains in a stationary position locked to the press framework 234, with idler gears 226 engaged with drive ring gear 218, and idler gears 228 engaged with inner driven gear 220. Thus, the inner driven gear and the small sprocket wheel 196 are driven at twice the speed of outer drive ring gear 220 and large sprocket wheel 196 when drive shaft 223 is coupled to a drive motor (not shown). As a result, inner platen support chains 198 travel the same distance as outer platen support chains 194, thereby providing a two-opening press. If the clutch plate 224 is engaged in its second position, the clutch plate is free to rotate with the center drive shaft 222, with the idler gears 226 and 228 locked to the inner driven gear 220. In this arrangement, the large sprocket wheel 192 and the small sprocket wheel 196 rotate together as a unit, and as a result, the outer platen support chains 194 travel twice the distance of the inner platen support chains 194, thereby providing a fouropening press.

lclaim:

1. An improved press comprising:

a. a supporting framework;

b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface;

c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, the upper platen and the center platen cooperating to define an upper workspace adapted to receive objects to be pressed;

d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, the lower platen and the center platen cooperating to define a lower workspace edapted to receive objects to be pressed;

e. platen support means movably supporting the upper and the lower platen from the framework, the support means including an upper sprocket wheel above the upper movable platen; a lower sprocket wheel below the lower movable platen; and an endless chain engaging the sprocket wheels and secured to the upper and lower movable platens, so that the weight of the upper platen is substantially balanced by the weight of the lower platen; and

f. drive means for simultaneously forcing the upper platen down and the lower platen up toward the center platen to apply substantially the same pressure to the objects disposed within the workspaces, irrespective of the weight of the movable platens.

2. The improvement according to claim 1 wherein the drive means includes a motor coupled to the upper sprocket wheel for moving the movable platens toward the center platen, and hydraulic means secured to the framework and coupled to each movable platen, the hydraulic means being operable independently of the motor for moving the movable platens toward the center platen.

3. An improved press comprising:

a. a supporting framework;

b. a substantially horizontal stationary platen secured to the framework and having an upper surface and a lower surface;

c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, and an upper intermediate movable platen disposed between and substantially parallel to the center' platen and the upper movable platen; the upper movable platens cooperating with the center platen to define a pair of upper workspaces for objects to be pressed;

(1. a lower movable platen disposed substantially parallel to the lower surface of the center platen, and a lower intermediate movable platen disposed between and substantially parallel to the center platen and the lower movable platen, the lower movable platens cooperating with the center platen to define a pair of lower workspaces for objects to be pressed;

e. means for supporting the upper and lower movable platens from the framework, the support means including a first upper sprocket wheel mounted for rotation above the upper movable platen, a first lower sprocket wheel mounted for rotation below the lower movable platen, and a first endless chain engaging the first sprocket wheels and secured to the upper and lower movable platens so that the weight of the upper platen is substan tially balanced by the weight of the lower platen; means for supporting the upper and lower intermediate movable platens from the framework, the support means including a second upper sprocket wheel having a diameter less than that of the first upper sprocket wheel adapted to rotate with said first upper sprocket wheel, a second lower sprocket wheel having a diameter less than that of the first lower sprocket wheel adapted to rotate with said first lower sprocket wheel, and a second endless chain engaging the second sprocket wheels and secured to the upper and lower intermediate movable platens so that the weight of the upper intermediate platen is substantially balanced by the weight of the lower inter mediate platen; and

. drive means for simultaneously forcing the upper platens down and the lower platens up toward the center platen to apply substantially the same pressure to the objects disposed within the workspaces, irrespective of the weight of the movable platens.

4. The improvement according to claim 3 wherein the drive means includes a motor coupled to the upper sprocket wheels for moving the movable platens toward the center platen, and hydraulic means secured to the framework and coupled to the upper and lower movable platens, the hydraulic means being operable independently of the motor for moving the movable platens toward the center platens.

5. The improvement according to claim 1 including means for heating the center platen and the movable platens to substantially equal temperatures so that heat is uniformly applied to the objects in the workspaces.

6. The improvement according to claim I wherein the platen support means includes a second upper sprocket wheel above the upper movable platen and spaced laterally from the other upper sprocket wheel; a second lower sprocket wheel below the lower movable platen and spaced laterally from the other lower sprocket wheel; and an endless chain coupled with the upper sprocket wheels for use in maintaining horizontal alignment of the movable platens during operation of the drive means.

7. The improvement according to claim 3 including means for heating the center platen and the movable platens to substantially equal temperatures so that the heat is uniformly applied to the objects in the workspaces.

8. The improvement according to claim 3 including a third upper sprocket wheel mounted for rotation above the upper movable platen and spaced laterally from the first upper sprocket wheel; a third lower sprocket wheel mounted for rotation below the lower movable platen and spaced laterally from the first lower sprocket wheel; a third endless chain engaging the third sprocket wheels and secured to the upper and lower movable platens so that the weight of the upper platen is substantially balanced by the weight of the lower platen; a fourth upper sprocket wheel having a diameter less than that of the third upper sprocket wheel adapted to rotate with said third upper sprocket wheel; a fourth lower sprocket wheel having a diameter less than that of the third lower sprocket wheel and adapted to rotate with said third lower sprocket wheel; a fourth endless chain engaging the fourth sprocket wheels and secured to the upper and lower intermediate movable platens so that the weightof the upper intermediate platen is substantially balanced by the weight of the lower intermediate platen; and an endless chain coupled with the first and second upper sprocket wheels on the one hand and the third and fourth upper sprocket wheels on the other hand for use in maintaining horizontal alignment of the movable platens during operation of the drive means.

9. An improved press comprising:

a. a supporting framework;

b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface;

c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, and an upper intermediate movable platen disposed between and substantially parallel to the center platen and the upper movable platen; the upper movable platens cooperating with the center platen to define a pair of upper workspaces for objects to be pressed;

d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, and a lower intermediate movable platen disposed between and substantially parallel to the center platen and the lower movable platen, the lower movable platens cooperating with the center platen to define a pair of lower workspaces for objects to be pressed;

. means for movably supporting the upper and lower movable platens from the framework so that the weight of the upper movable platen is substantially balanced by the weight of the lower movable platen, the support means including a first sprocket wheel rotatably mounted above the upper movable platen, and a chain engaging the sprocket wheel and secured at one end to the upper movable platen and at the other end to the lower movable platen;

f. means for movably supporting the upper and lower intermediate movable platens from the framework so that the weight of the upper intermediate platen is substantially balanced by the weight of the lower intermediate platen, the support means including a second sprocket wheel rotatably mounted above the upper movable platen such that it rotates independently of the first sprocket wheel, and a second chain engaging the second sprocket wheel and secured at one end to the upper intermediate platen and at its other end to the lower intermediate platen; and

g. drive means for moving the pair of upper and lower movable platens on the one hand and the intermediate platens on the other hand toward the center platen in sequence to apply substantially the same pressure to the objects disposed within the workspaces, irrespective of the weight of the movable platens.

10. The improvement according to claim 8 wherein the drive means is adapted to move the upper and lower platens away from the center platen after applying pressure to the objects in the workspaces; and including lifting means secured to the upper platen for moving the upper intermediate platen away from the center platen as the drive means moves the upper platen away from the center platen,

11. An improved press comprising:

a. a supporting framework;

b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface;

c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, the upper platen and the center platen cooperating to define an upper workspace adapted to receive objects to be pressed;

d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, the lower platen and the center platen cooperating to define a lower workspace adapted to receive objects to be pressed;

e. platen support means for movably supporting the upper and lower platens from the framework so that the weight of the upper platen is substantially balanced by the weight of the lower platen, the platen support means including a first sprocket wheel rotatably mounted above the upper movable platen, a chain engaging the first sprocket wheel and secured at one end to the upper movable platen and at the other end at the lower movable platen, a second sprocket wheel rotatably mounted above the upper movable platen and spaced laterally from the first sprocket wheel, a chain engaging the second sprocket wheel and secured at one end to the upper movable platen and at the other end at the lower movable platen, and a substantially horizontally disposed endless chain engaged with the first and second sprocket wheels; and

f. drive means for simultaneously forcing the upper platen down and the lower platen up toward the center platen to apply substantially the same pressure to the objects disposed within the workspaces, irrespective of the weight of the movable platens, the horizontal endless chain being useful in maintaining horizontal alignment of the movable platens during operation of the drive means.

12. An improved press comprising:

a. a supporting framework having a front side and a rear side;

b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface;

c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, the upper platen and the center platen cooperating to define an upper workspace adapted to receive objects to be pressed;

d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, the lower platen and the center platen cooperating to define a lower workspace adapted to receive objects to be pressed;

e, platen support means for movably supporting the. upper and lower platens from the framework so that the weight of the upper platen is substantially balanced by the weight of the lower platen, the platen support means including a pair of laterally spaced apart front sprocket wheels on the front side of the framework above the upper movable platen, a pair of laterally spaced apart rear sprocket wheels on the rear side of the framework above the upper movable platen; a separate chain engaged with each front sprocket wheel and secured at one point to the upper movable platen and at another point to the lower movable platen; a separate rear chain engaged with each rear sprocket wheel and secured at one point to the upper movable platen and at another point to the lower movable platen; and

f. drive means for simultaneously forcing the upper platen down and the lower platen up toward the center platen to apply substantially the same pressure to the objects disposed within the workspaces, irrespective of the weight of the movable platens.

3. The improvement according to claim 12 in which the drive means includes a substantially horizontally disposed endless chain engaged with the front pair of sprocket wheels, and a separate horizontally disposed endless chain engaged with the rear pair of sprocket wheels, whereby the horizontal endless chains are useful in maintaining horizontal alignment of the movable platens during operation of the drive means. 14. The improvement according to claim 13 in which one from sprocket wheel is aligned longitudinally with a respective one of the rear sprocket wheels, and the other front sprocket wheel is aligned longitudinally with the remaining rear sprocket wheel; and including a pair of elongated rotatable shafts coupling the aligned pairs of front and rear sprocket wheels.

15. The improvement according to claim 14 including a drive motor coupled to at least one of said shafts for rotating said shaft and said front and rear sprocket wheels to drive the movable platens toward the center platen.

16. The improvement according to claim 15 including hydraulic means secured to the framework and coupled to each movable platen, the hydraulic means being operable independently of the motor for driving the movable platens toward the center platen.

17. An improved press comprising:

a. a supporting framework;

b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface;

c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, and an upper intermediate movable platen disposed between and substantially parallel to the center platen and the upper movable platen; the upper movable platens cooperating with the center platen to define a pair of upper workspaces for objects to be pressed;

d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, and a lower intermediate movable platen disposed between and substantially parallel to the center platen and the lower movable platen, the lower movable platens cooperating with the center platen to define a pair of lower workspaces for objects to be pressed;

e. platen support means for movably supporting the movable platens from the framework so that the weight of the upper movable platen is substantially balanced by the weight of the lower movable platen, and the weight of the upper intermediate platen is substantially balanced by the weight of the lower intermediate platen; and drive means adapted to force the upper and lower movable platens and the intermediate movable platens toward the center platen to apply substantially the same pressure to the objects disposed within the workspaces irrespective of the weight of the movable platens, the drive means including means for permitting the intermediate movable platens to move toward and away from the center platen independently of the upper and lower movable platens, so as to provide enlarged upper and lower workspaces within the press.

18. An improved press comprising: a. a supporting framework; b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface;

c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, and an upper intermediate movable platen disposed between and substantially parallel to the center platen and the upper movable platen; the upper movable platens cooperating with the center platen to define a pair of upper workspaces for objects to be pressed;

d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, and a lower intermediate moveable platen disposed between and substantially parallel to the center platen and the lower movable platen, the lower movable platens cooperating with the center platen to define a pair of lower workspaces for objects to be pressed;

first and second support means for movably supporting the upper and lower movable platens, and the intermediate movable platens, respectively, from the framework so that the weight of the upper movable platen is substantially balanced by the weight of the lower platen, and the weight of the upper intermediate movable platen is substantially balanced by the weight of the lower movable intermediate platen; and

f. adjustable drive means either for forcing the intermediate movable platens toward the center platen at the same rate of speed as the upper and lower movable platens, or for forcing the intermediate movable platens toward the center platen at a lower rate of speed than the upper and lower movable platens to provide either a two-opening press or a four-opening press, respectively, to apply substantially the same pressure to the objects disposed within the openings of the press, irrespective of the weight of the movable platens.

19. The improvement according to claim 18 in which the first platen support means includes a first upper sprocket wheel mounted for rotation about the upper movable platen, a first lower sprocket wheel mounted for rotation below the lower movable platen, a first endless chain engaging the first sprocket wheels and secured to the upper and lower movable platens so that the weight of the upper platen is substantially balanced by the weight of the lower platen; and'wherein the second platen support means includes a second upper sprocket wheel having a diameter less than that of the first sprocket wheel, the second upper sprocket wheel being adapted to rotate with said first upper sprocket wheel, a second lower sprocket wheel having a diameter less than that of the first lower sprocket wheel, the second lower sprocket wheel being adapted to rotate with said first lower sprocket wheel, and a second endless chain engaging the second sprocket wheels and secured to the upper and lower intermediate platens so that the weight of the upper intermediate platen is substantially balanced by the weight of the lower in termediate platen; and in which the adjustable drive means includes clutch means adapted to adjust the relative rates of rotation of the first and second sprocket wheels.

20. An improved press comprising:

a. a supporting framework;

b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface;

c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, and an upper intermediate movable platen disposed between and substantially parallel to the center platen and the upper movable platen; the upper movable-platens cooperating with the center platen to define a pair of upper workspaces for objects to be pressed; d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, and a lower intermediate movable platen disposed between and substantially parallel to the center platen and the lower movable platen, the lower movable platens cooperating with the center platen to define a pair of lower workspaces for objects to be pressed;

e. means for supporting the upper and lower movable platens from the framework, the support means including a first upper sprocket wheel mounted for rotation above the upper movable platen, a first lower sprocket wheel mounted for rotation below the lower movable platen, and a first endless chain engaging the first sprocket wheels and secured to the upper and lower movable platens so that the weight of the upper platen is substantially balanced by the weight of the lower platen;

f. means for supporting the upper and lower intermediate movable platens from the framework, the support means including a second upper sprocket wheel having a diameter less than that of the first sprocket wheel and adapted to rotate independently of said first sprocket wheel, a

. drive means for forcing the upper and lower movable platens and the intermediate platen toward the center platen in sequence to apply substantially the same pressure to objects disposed within the workspaces, irrespective of the weight of the movable platens.

P0-1050 UNITED STATES PATENT OFFICE (st/F9) CERTIFICATE OF CORRECTION Patent No- 3 a 638,559 bated February 1, 1972 RUSSELL A. PARKER Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 12, line 7, "8" should read --9--. (Claim .10)

C01. l3, line 10, claim number "3" should read '-l3.,---. {Claiml3) Signed and sealed this 20th day of June 1972.

(SEAL) AttGS-ti EDWARD M.FLETCHEE, JR. RQBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

1. An improved press comprising: a. a supporting framework; b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface; c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, the upper platen and the center platen cooperating to define an upper workspace adapted to receive objects to be pressed; d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, the lower platen and the center platen cooperating to define a lower workspace adapted to receive objects to be pressed; e. platen support means movably supporting the upper and the lower platen from the framework, the support means including an upper sprocket wheel above the upper movable platen; a lower sprocket wheel below the lower movable platen; and an endless chain engaging the sprocket wheels and secured to the upper and lower movable platens, so that the weight of the upper platen is substantially balanced by the weight of the lower platen; and f. drive means for simultaneously forcing the upper platen down and the lower platen up toward the center platen to apply substantially the same pressure to the objects disposed within the workspaces, irrespective of the weight of the movable platens.
 2. The improvement according to claim 1 wherein the drive means includes a motor coupled to the upper sprocket wheel for moving the movable platens toward the center platen, and hydraulic means secured to the framework and coupled to each movable platen, the hydraulic means being operable independently of the motor for moving the movable platens toward the center platen.
 3. An improved press comprising: a. a supporting framework; b. a substantially horizontal stationary platen secured to the framework and having an upper surface and a lower surface; c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, and an upper intermediate movable platen disposed between and substantially parallel to the center platen and the upper movable platen; the upper movable platens cooperating with the center platen to define a pair of upper workspaces for objects to be pressed; d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, and a lower intermediate movable platen disposed between and substantially parallel to the center platen and the lower movable platen, the lower movable platens cooperating with the center platen to define a pair of lower workspaces for objects to be pressed; e. means for supporting the upper and lower movable platens from the framework, the support means including a first upper sprocket wheel mounted for rotation above the upper movable platen, a first lower sprocket wheel mounted for rotation below the lower movable platen, and a first endless chain engaging the first sprocket wheels and secured to the upper and lower movable platens so that the weight of the upper platen is substantially balanced by the weight of the lower platen; f. means for supporting the upper and lower intermediate movable platens from the framework, the support means including a second upper sprocket wheel having a diameter less than that of the first upper sprocket wheel adapted to rotate with said first upper sprocket wheel, a second lower sprocket wheel having a diameter less than that of the first lower sprocket wheel adapted to rotate with said first lower sprocket wheel, and a second endless chain engaging the second sprocket wheels and secured to the upper and lower intermediate movable platens so that the weight of the upper intermediate platen is substantially balanced by the weight of the lower intermediate platen; and g. drive means for simultaneously forcing the upper platens down and the lower platens up toward the center platen to apply substantially the same pressure to the objects disposed within the workspaces, irrespective of the weight of the movable platens.
 3. The improvement according to claim 12 in which the drive means includes a substantially horizontally disposed endless chain engaged with the front pair of sprocket wheels, and a separate horizontally disposed endless chain engaged with the rear pair of sprocket wheels, whereby the horizontal endless chains are useful in maintaining horizontal alignment of the movable platens during operation of the drive means.
 4. The improvement according to claim 3 wherein the drive means includes a motor coupled to the upper sprocket wheels for moving the movable platens toward the center platen, and hydraulic means secured to the framework and coupled to the upper and lower movable platens, the hydraulic means being operable independently of the motor for moving the movable platens toward the center platens.
 5. The improvement according to claim 1 including means for heating the center platen and the movable platens to substantially equal temperatures so that heat is uniformly applied to the objects in the workspaces.
 6. The improvement according to claim 1 wherein the platen support means includes a second upper sprocket wheel above the upper movable platen and spaced laterally from the other upper sprocket wheel; a second lower sprocket wheel below the lower movable platen and spaced laterally from the other lower sprocket wheel; and an endless chain coupled with the upper sprocket wheels for use in maintaining horizontal alignment of the movable platens during operation of the drive means.
 7. The improvement according to claim 3 including means for heating the center platen and the movable platens to substantially equal temperatures so that the heat is uniformly applied to the objects in the workspaces.
 8. The improvement according to claim 3 including a third upper sprocket wheel mounted for rotation above the upper movable plAten and spaced laterally from the first upper sprocket wheel; a third lower sprocket wheel mounted for rotation below the lower movable platen and spaced laterally from the first lower sprocket wheel; a third endless chain engaging the third sprocket wheels and secured to the upper and lower movable platens so that the weight of the upper platen is substantially balanced by the weight of the lower platen; a fourth upper sprocket wheel having a diameter less than that of the third upper sprocket wheel adapted to rotate with said third upper sprocket wheel; a fourth lower sprocket wheel having a diameter less than that of the third lower sprocket wheel and adapted to rotate with said third lower sprocket wheel; a fourth endless chain engaging the fourth sprocket wheels and secured to the upper and lower intermediate movable platens so that the weight of the upper intermediate platen is substantially balanced by the weight of the lower intermediate platen; and an endless chain coupled with the first and second upper sprocket wheels on the one hand and the third and fourth upper sprocket wheels on the other hand for use in maintaining horizontal alignment of the movable platens during operation of the drive means.
 9. An improved press comprising: a. a supporting framework; b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface; c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, and an upper intermediate movable platen disposed between and substantially parallel to the center platen and the upper movable platen; the upper movable platens cooperating with the center platen to define a pair of upper workspaces for objects to be pressed; d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, and a lower intermediate movable platen disposed between and substantially parallel to the center platen and the lower movable platen, the lower movable platens cooperating with the center platen to define a pair of lower workspaces for objects to be pressed; e. means for movably supporting the upper and lower movable platens from the framework so that the weight of the upper movable platen is substantially balanced by the weight of the lower movable platen, the support means including a first sprocket wheel rotatably mounted above the upper movable platen, and a chain engaging the sprocket wheel and secured at one end to the upper movable platen and at the other end to the lower movable platen; f. means for movably supporting the upper and lower intermediate movable platens from the framework so that the weight of the upper intermediate platen is substantially balanced by the weight of the lower intermediate platen, the support means including a second sprocket wheel rotatably mounted above the upper movable platen such that it rotates independently of the first sprocket wheel, and a second chain engaging the second sprocket wheel and secured at one end to the upper intermediate platen and at its other end to the lower intermediate platen; and g. drive means for moving the pair of upper and lower movable platens on the one hand and the intermediate platens on the other hand toward the center platen in sequence to apply substantially the same pressure to the objects disposed within the workspaces, irrespective of the weight of the movable platens.
 10. The improvement according to claim 8 wherein the drive means is adapted to move the upper and lower platens away from the center platen after applying pressure to the objects in the workspaces; and including lifting means secured to the upper platen for moving the upper intermediate platen away from the center platen as the drive means moves the upper platen away from the center platen.
 11. An improved press comprising: a. a supporting framework; b. a substantially horizontal stationary center platen secured to the framework anD having an upper surface and a lower surface; c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, the upper platen and the center platen cooperating to define an upper workspace adapted to receive objects to be pressed; d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, the lower platen and the center platen cooperating to define a lower workspace adapted to receive objects to be pressed; e. platen support means for movably supporting the upper and lower platens from the framework so that the weight of the upper platen is substantially balanced by the weight of the lower platen, the platen support means including a first sprocket wheel rotatably mounted above the upper movable platen, a chain engaging the first sprocket wheel and secured at one end to the upper movable platen and at the other end at the lower movable platen, a second sprocket wheel rotatably mounted above the upper movable platen and spaced laterally from the first sprocket wheel, a chain engaging the second sprocket wheel and secured at one end to the upper movable platen and at the other end at the lower movable platen, and a substantially horizontally disposed endless chain engaged with the first and second sprocket wheels; and f. drive means for simultaneously forcing the upper platen down and the lower platen up toward the center platen to apply substantially the same pressure to the objects disposed within the workspaces, irrespective of the weight of the movable platens, the horizontal endless chain being useful in maintaining horizontal alignment of the movable platens during operation of the drive means.
 12. An improved press comprising: a. a supporting framework having a front side and a rear side; b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface; c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, the upper platen and the center platen cooperating to define an upper workspace adapted to receive objects to be pressed; d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, the lower platen and the center platen cooperating to define a lower workspace adapted to receive objects to be pressed; e. platen support means for movably supporting the upper and lower platens from the framework so that the weight of the upper platen is substantially balanced by the weight of the lower platen, the platen support means including a pair of laterally spaced apart front sprocket wheels on the front side of the framework above the upper movable platen, a pair of laterally spaced apart rear sprocket wheels on the rear side of the framework above the upper movable platen; a separate chain engaged with each front sprocket wheel and secured at one point to the upper movable platen and at another point to the lower movable platen; a separate rear chain engaged with each rear sprocket wheel and secured at one point to the upper movable platen and at another point to the lower movable platen; and f. drive means for simultaneously forcing the upper platen down and the lower platen up toward the center platen to apply substantially the same pressure to the objects disposed within the workspaces, irrespective of the weight of the movable platens.
 14. The improvement according to claim 13 in which one front sprocket wheel is aligned longitudinally with a respective one of the rear sprockeT wheels, and the other front sprocket wheel is aligned longitudinally with the remaining rear sprocket wheel; and including a pair of elongated rotatable shafts coupling the aligned pairs of front and rear sprocket wheels.
 15. The improvement according to claim 14 including a drive motor coupled to at least one of said shafts for rotating said shaft and said front and rear sprocket wheels to drive the movable platens toward the center platen.
 16. The improvement according to claim 15 including hydraulic means secured to the framework and coupled to each movable platen, the hydraulic means being operable independently of the motor for driving the movable platens toward the center platen.
 17. An improved press comprising: a. a supporting framework; b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface; c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, and an upper intermediate movable platen disposed between and substantially parallel to the center platen and the upper movable platen; the upper movable platens cooperating with the center platen to define a pair of upper workspaces for objects to be pressed; d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, and a lower intermediate movable platen disposed between and substantially parallel to the center platen and the lower movable platen, the lower movable platens cooperating with the center platen to define a pair of lower workspaces for objects to be pressed; e. platen support means for movably supporting the movable platens from the framework so that the weight of the upper movable platen is substantially balanced by the weight of the lower movable platen, and the weight of the upper intermediate platen is substantially balanced by the weight of the lower intermediate platen; and f. drive means adapted to force the upper and lower movable platens and the intermediate movable platens toward the center platen to apply substantially the same pressure to the objects disposed within the workspaces irrespective of the weight of the movable platens, the drive means including means for permitting the intermediate movable platens to move toward and away from the center platen independently of the upper and lower movable platens, so as to provide enlarged upper and lower workspaces within the press.
 18. An improved press comprising: a. a supporting framework; b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface; c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, and an upper intermediate movable platen disposed between and substantially parallel to the center platen and the upper movable platen; the upper movable platens cooperating with the center platen to define a pair of upper workspaces for objects to be pressed; d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, and a lower intermediate moveable platen disposed between and substantially parallel to the center platen and the lower movable platen, the lower movable platens cooperating with the center platen to define a pair of lower workspaces for objects to be pressed; e. first and second support means for movably supporting the upper and lower movable platens, and the intermediate movable platens, respectively, from the framework so that the weight of the upper movable platen is substantially balanced by the weight of the lower platen, and the weight of the upper intermediate movable platen is substantially balanced by the weight of the lower movable intermediate platen; and f. adjustable drive means either for forcing the intermediate movable platens toward the center platen at the same rate of speed as the upper and lower movable platens, or for forciNg the intermediate movable platens toward the center platen at a lower rate of speed than the upper and lower movable platens to provide either a two-opening press or a four-opening press, respectively, to apply substantially the same pressure to the objects disposed within the openings of the press, irrespective of the weight of the movable platens.
 19. The improvement according to claim 18 in which the first platen support means includes a first upper sprocket wheel mounted for rotation about the upper movable platen, a first lower sprocket wheel mounted for rotation below the lower movable platen, a first endless chain engaging the first sprocket wheels and secured to the upper and lower movable platens so that the weight of the upper platen is substantially balanced by the weight of the lower platen; and wherein the second platen support means includes a second upper sprocket wheel having a diameter less than that of the first sprocket wheel, the second upper sprocket wheel being adapted to rotate with said first upper sprocket wheel, a second lower sprocket wheel having a diameter less than that of the first lower sprocket wheel, the second lower sprocket wheel being adapted to rotate with said first lower sprocket wheel, and a second endless chain engaging the second sprocket wheels and secured to the upper and lower intermediate platens so that the weight of the upper intermediate platen is substantially balanced by the weight of the lower intermediate platen; and in which the adjustable drive means includes clutch means adapted to adjust the relative rates of rotation of the first and second sprocket wheels.
 20. An improved press comprising: a. a supporting framework; b. a substantially horizontal stationary center platen secured to the framework and having an upper surface and a lower surface; c. an upper movable platen disposed substantially parallel to the upper surface of the center platen, and an upper intermediate movable platen disposed between and substantially parallel to the center platen and the upper movable platen; the upper movable platens cooperating with the center platen to define a pair of upper workspaces for objects to be pressed; d. a lower movable platen disposed substantially parallel to the lower surface of the center platen, and a lower intermediate movable platen disposed between and substantially parallel to the center platen and the lower movable platen, the lower movable platens cooperating with the center platen to define a pair of lower workspaces for objects to be pressed; e. means for supporting the upper and lower movable platens from the framework, the support means including a first upper sprocket wheel mounted for rotation above the upper movable platen, a first lower sprocket wheel mounted for rotation below the lower movable platen, and a first endless chain engaging the first sprocket wheels and secured to the upper and lower movable platens so that the weight of the upper platen is substantially balanced by the weight of the lower platen; f. means for supporting the upper and lower intermediate movable platens from the framework, the support means including a second upper sprocket wheel having a diameter less than that of the first sprocket wheel and adapted to rotate independently of said first sprocket wheel, a second lower sprocket wheel having a diameter less than that of the first lower sprocket wheel and adapted to rotate independently of said first lower sprocket wheel, and a second endless chain engaging the second sprocket wheels and secured to the upper and lower intermediate movable platens so that the weight of the upper intermediate platen is substantially balanced by the weight of the lower intermediate platen; and g. drive means for forcing the upper and lower movable platens and the intermediate platen toward the center platen in sequence to apply substantially the same pressure to objects disposed within the workspaces, irrespective of the weight of the movable platens. 